May 2 (Reuters) - Fortinet forecast second-quarter billings below Wall Street estimates on Thursday, hurt by muted enterprise spending and stiff competition from companies that act as one-stop shops for cybersecurity tools.

Shares of the Sunnyvale, California-based company fell about 8% in trading after the bell.

High-interest rates have crimped enterprise spending as businesses grapple with economic uncertainty and look to preserve cash balances.

The company expects second-quarter billings between $1.49 billion and $1.55 billion, largely below analysts' estimates of $1.54, according to LSEG data.

Billings are the invoice amounts billed to customers in a given time period. Analysts use billings to determine cash flow as they represent money the company expects to receive soon.

It reported billings of $1.41 billion, down 6.4% in the first quarter, compared with estimates of $1.43 billion.

Meanwhile, Fortinet's rivals, such as Palo Alto Networks and Crowdstrike Holdings, have gained market share in the past year as companies have been adopting more efficient and less expensive consolidated cybersecurity platforms that contain tools for a variety of applications.

Fortinet expects second-quarter revenue between $1.375 billion and $1.435 billion, compared with analysts' estimates of $1.39 billion, according to LSEG data.

It posted revenue of $1.35 billion in the first quarter, up 7.2%, just about beating estimates of $1.34 billion.

Adjusted profit in the first quarter stood at 43 cents per share, compared with estimates of 38 cents per share. (Reporting by Akash Sriram in Bengaluru; Editing by Tasim Zahid)